Analysis of spectrum efficiency and energy efficiency interrelationship in heterogeneous cellular networks

This paper addresses the problem of balancing the tradeoff between spectrum efficiency (SE) and energy efficiency (EE) in heterogeneous cellular networks (HetNets). A framework is developed for analyzing the SE and EE of a 2-tier HetNet consisting of macro and femtocell base stations (BS) with shared spectrum operation. From the analysis it is shown that both the SE and EE can be significantly enhanced with the overlaid deployment of the femto tier. However, the performance gain achievable is found to be strongly dependent on the load level and the BS power consumption attributes. A multi-objective optimization problem that maximizes the SE and EE subject to Quality of Service (QoS) constraints is formulated and solved to give the Pareto optimal operational regime. In contrast to the conventional approach, this paper quantifies the SE-EE tradeoff as a Lebesgue measure, defined by the Pareto optimal regime. Numerical results show that while the performance improvement achieved by balancing the SE-EE tradeoff is marginal under high load conditions, it is feasible to significantly increase the SE and EE during low load conditions and satisfy the users´ QoS requirements by optimally adapting the network configuration.